Thanks Auto.
That's a concise and fantastic summary! I have a low-mileage '70 1/2 Z28/M21 that I bought new. In the late seventies I swapped in a 495" aluminum Can Am engine but parked it not long after. It's now going back together with a Jones solid roller and a number of other changes that should add up to ~750 HP/675 lb-ft.
I've experienced wearisomely overtaxed trannys before (e.g. 215" Buick-powered Beetle) and assumed I'd need an alternative box to enjoy my ride, (I scored a Crovetter ZF 6 speed, but then realized I'd have to take an ax to the floorpan to fit it.) but it sounds like your M23 should handle it just fine and would be a simple drop-in. Hmmm... maybe I could re-stamp it and retain the 'all but engine numbers-matching' status..

An M23 (2.20/1.64/1.27/1.00) or one of the M23W's (2.56/1.75/1.36/1.00 or 2.56/1.90/1.36 or maybe even 2.56/1.61/1.26/1.00) would fit the bill nicely. Your shifter, driveshaft, slipyoke, bellhousing, etc can all be retained if you like.

You can get an M23-series gearbox from Medatronics (5speeds.com), Jody's Transmissions, us, Midwest Muncies; or I may have a smaller distributor local to you.

We did. It was Nodular Iron and cast in several US locations over its life. However, as the M23-platform has increased in scope, we needed an updated design. The new design has the mainshaft bearing bore flipped over; to more adequately support the snapring groove. The dimensions were changed to eliminate the (2) high crush gaskets (even our gaskets are made in America from gasket material designed for Abrams tanks). Eliminating the gaskets means less chance of misalignment between the mainshaft and the rear bushing in the tailhousing (the bushing in our tailhousing is an OE bushing that is designed to be reamed-in-place, not a fits-all service replacement bushing). In order to go to the "gasket-less" junctions between the 3 main castings, they all SHOULD be of similar material. We originally looked at 357-series aluminum, but this has beryllium copper (BeCu) in the composition, which is bad juju for machinists. C355 is what Dart uses for their Pro-1 cylinder heads, and their aluminum engine blocks. It is approximately 20% stronger than the 356-series aluminum we use for our legendary SuperCase. Our C355 aluminum midplate is half the weight of the nodular iron; and cheaper to boot. Still cast and machined in the US of A.

Autogear... can you explain more about the "gasketless junctions?" How are you sealing this thing?

EDIT: Looked at your site, and I really hate the idea of "N-series" components replacing the good backwards-compatible stuff. Guess this means resto guys will have to resort to offshore junk in the future?

novadude wrote:Autogear... can you explain more about the "gasketless junctions?" How are you sealing this thing?

EDIT: Looked at your site, and I really hate the idea of "N-series" components replacing the good backwards-compatible stuff. Guess this means resto guys will have to resort to offshore junk in the future?

You need a TIG welder and a steady hand...
Kidding. I should have said "no more paper gaskets between the tailhousing, midplate and case." Paper gaskets impart a lot of variation due to humidity changes. They require a certain amount of crush and create the ability for the parts to move slightly, independent of each other. We use Valco import grey RTV applied in a very fine bead with their "tube grip" pliers. You could use an anerobic sealant, which would make an even stronger joint, and a more rigid transmission.

I understand the desire to keep the OE-style (what we call the M-series) reverse geartrain, mainshaft and hubs. Please understand the N-series is being developed to carry our flagship product into the future. Similarly, no one expects every Jerico part to fit their 64 Falcon toploader.

* We will still carry the traditional Muncie hubs. Both the standard diameter, hardened hub and the slightly oversized hardened hub (that will only fit a OE Spec dimension slider - no cheap sliders here); made in Italy.
* We will still carry the traditional Muncie reverse geartrain; made in Italy.
* We will still carry the forged, plug quenched sliders; both the stock style 36-spline, and the "Torq-Lock" 36-spline. Made in Italy
*We will still carry the forged 18-spline, plug quenched lightweight sliders. This is a double broached 18-spline slider, that is then properly heat treated. It is NOT a hardened 36-spline stock slider that has been modified by grinding away the splines. Made in Italy.

****The ONLY thing that will be left behind is the AG Muncie-style lightweight mainshafts. These are gundrilled at the factory under the forward gears (the hole stops under the 1st gear journal) before they're hardened. Made in Italy. I have about 300 of each (27 and 32 spline) to be sold.
George has been working here since Muncies were cutting edge technology. Muncie mainshafts were almost never sold over the counter ("I don't really remember selling more than 25 a year back in the '70s" - George). They are very durable. In addition, very often the large reverse gear, and its mating gear are replaced as standard practice in Muncies. So if you HAD to replace a mainshaft, chances are the reverse geartrain was replaced at the same time. That leaves the only "extra" N-series parts being the sm. reverse idler and the hubs. You can re-use your sliders if they're still sound.
The majority of the mainshafts we sell today are for the construction of new gearboxes; in which case, you need the reverse geartrain and hubs.
Worst case scenario, you may need to source a Muncie mainshaft; or purchase an OE-style Italian one and stick it on the shelf. Everything else will remain produced in Italy and sold through our distributors, or factory direct.

Thanks for the clarification. From what I read, it was not entirely clear that everything but the mainshaft would still be available for the traditional Muncie, that you would still be carrying the "old style" hubs / sliders, and that all other "new" parts would fit old cases.

No worries; thats what Im here for. We try to publish charts and descriptions that are easy - but at the end of the day, we are gear guys; and look at this stuff for weeks straight before its released...it always makes sense to US because we see what we want it to say.

novadude wrote:Autogear... can you explain more about the "gasketless junctions?" How are you sealing this thing?

EDIT: Looked at your site, and I really hate the idea of "N-series" components replacing the good backwards-compatible stuff. Guess this means resto guys will have to resort to offshore junk in the future?

You need a TIG welder and a steady hand...
Kidding. I should have said "no more paper gaskets between the tailhousing, midplate and case." Paper gaskets impart a lot of variation due to humidity changes. They require a certain amount of crush and create the ability for the parts to move slightly, independent of each other. We use Valco import grey RTV applied in a very fine bead with their "tube grip" pliers. You could use an anerobic sealant, which would make an even stronger joint, and a more rigid transmission.

I understand the desire to keep the OE-style (what we call the M-series) reverse geartrain, mainshaft and hubs. Please understand the N-series is being developed to carry our flagship product into the future. Similarly, no one expects every Jerico part to fit their 64 Falcon toploader.

* We will still carry the traditional Muncie hubs. Both the standard diameter, hardened hub and the slightly oversized hardened hub (that will only fit a OE Spec dimension slider - no cheap sliders here); made in Italy.
* We will still carry the traditional Muncie reverse geartrain; made in Italy.
* We will still carry the forged, plug quenched sliders; both the stock style 36-spline, and the "Torq-Lock" 36-spline. Made in Italy
*We will still carry the forged 18-spline, plug quenched lightweight sliders. This is a double broached 18-spline slider, that is then properly heat treated. It is NOT a hardened 36-spline stock slider that has been modified by grinding away the splines. Made in Italy.

****The ONLY thing that will be left behind is the AG Muncie-style lightweight mainshafts. These are gundrilled at the factory under the forward gears (the hole stops under the 1st gear journal) before they're hardened. Made in Italy. I have about 300 of each (27 and 32 spline) to be sold.
George has been working here since Muncies were cutting edge technology. Muncie mainshafts were almost never sold over the counter ("I don't really remember selling more than 25 a year back in the '70s" - George). They are very durable. In addition, very often the large reverse gear, and its mating gear are replaced as standard practice in Muncies. So if you HAD to replace a mainshaft, chances are the reverse geartrain was replaced at the same time. That leaves the only "extra" N-series parts being the sm. reverse idler and the hubs. You can re-use your sliders if they're still sound.
The majority of the mainshafts we sell today are for the construction of new gearboxes; in which case, you need the reverse geartrain and hubs.
Worst case scenario, you may need to source a Muncie mainshaft; or purchase an OE-style Italian one and stick it on the shelf. Everything else will remain produced in Italy and sold through our distributors, or factory direct.

Nathan

Fwiw, Gast Air motors use, "cigarette pack", cellophane film as their end plate gaskets. I have over hauled several of them when I was gunning refractories because they were used on REED, "SOVA", and, "LOVA", gunite machines. Charlie and I trued up the plates very carefully using an 8" long Nickelson(Sp?) fine tooth triangle file and WD-40.

This is another of what I call, "a feelie", deal..

Now as for the Muncie 5-speed, I see that Tremac balloons out the tail housing to fit the 5th gear IF NOT MISTAKEN???

Do the same thing to a REAL Muncie and go!! Just keep it the same length as one is stock now and fit the cross member mount bolts like is done for a TH400. Hell, moving a cross member back to fit a REAL Muncie 5-speed would be a, "piece a cake"!!!

Can't fit bolts to install the new tail housing then use studs in the tail housing that tighten down from the front and not pointing to the rear of the new tail housing....

George, isn't it(?), I offer my BSME for FREE to be in on this!!

A 700+ torque handling 5-speed Muncie will be a game changer as I see it that will keep our old 1st/2nd/3rd Gen. Camaros alive!

Truth is you're trying to cram 5LB of poo into a 3LB bag. The reverse geartrain in a Muncie is a space hog; and the tunnels for these cars are not conducive to bulgy transmissions (Ford had the 'pregnant' toploader case in trucks).
The TKO has mainshaft 5th formed ON the mainshaft; and they swung the shift system over the top. Talk to Mopar guys about fitting a TKO in a stock application. If you didnt use a slip yoke, it might 'help' in some aspects. You do know some corvette guys use a TKO converted to sideshift?

in a sci-fi world; my PERSONAL choice would be a 3.x:1 1st, direct drive 5spd with a 2.97-3.23 rear axle would be everything I needed. (3.2/2.56/1.75/1.36/1.00) for all around ass kicking. Dead nuts smooth and quiet in high gear; GT style 2nd-5th, and enough 1st gear to run a high 2's rear axle. Road Racing could go with a 3.2/2.20/1.64/1.27/1.00 Dedicated drag racing could be 3.2/2.56/1.90/1.36/1.00.

Truth is you're trying to cram 5LB of poo into a 3LB bag. The reverse geartrain in a Muncie is a space hog; and the tunnels for these cars are not conducive to bulgy transmissions (Ford had the 'pregnant' toploader case in trucks).
The TKO has mainshaft 5th formed ON the mainshaft; and they swung the shift system over the top. Talk to Mopar guys about fitting a TKO in a stock application. If you didnt use a slip yoke, it might 'help' in some aspects. You do know some corvette guys use a TKO converted to sideshift?

in a sci-fi world; my PERSONAL choice would be a 3.x:1 1st, direct drive 5spd with a 2.97-3.23 rear axle would be everything I needed. (3.2/2.56/1.75/1.36/1.00) for all around ass kicking. Dead nuts smooth and quiet in high gear; GT style 2nd-5th, and enough 1st gear to run a high 2's rear axle. Road Racing could go with a 3.2/2.20/1.64/1.27/1.00 Dedicated drag racing could be 3.2/2.56/1.90/1.36/1.00.

Im just being a gear nerd

Nathan

Nathan,

Please send me a set of Muncie drawings and I will figure out how to do it! And my damned computer won't open pdf's!

And this is, "FREE for FREE", just like my 1st Gen. front 13" rotor/2-15/16" dia. big, single piston calipers, "pdqCBB" brake template that I have sent to a bunch a guys in the past.